French gold chronometer watch with Guillaume balance Circa 1935

Gold open faced keyless lever watch
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A very fine French 18K white and yellow gold keyless lever pocket chronometer made for the Besançon Observatory Timing Contest, circa 1935. Polished white gold case with yellow gold rims and bow, coin-edge band, the back with the initials DD in yellow gold. Hinged white gold cuvette with engraved Observatory inscription. Matte silver dial with radial blue Roman hours, an outer blue minute track, subsidiary seconds at 6 o’clock and blued steel Breguet hands. A rhodium-plated movement, 17 jewels, stamped with the Besançon viper’s head mark, straight-line lever escapement, Guillaume balance, blued steel Breguet balance spring, index regulator. Dial, cuvette and movement signed, case numbered.
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Diameter: 44.5 mm
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Signed: Breguet Paris
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The punch mark in form of a viper’s head is applied by the Observatory of Besançon on watches that were successful at the Timing Contest and received the Bulletin de Première class.